<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<style>
    /* body{
        margin: 0;
    }
    table{
        margin: 0 auto;
        width: 500px;
        border-spacing: 0;
    }
    .header{
        height: 50px;
        background: olive;
    }
    .aside{
        width: 50px;
        height: 60px;
        background: purple;
    }
    .section{
        width: 55px;
        height: 66px;
        background: maroon;
    }
    .footer{
        height: 80px;
        background: gray;
    } */
    body{
        width: 100px;
        margin: 0 auto;
        color: blue;
    }
    header{
        height: 50px;
        background: olive;
    }
    aside{
        width: 100px;
        height: 20px;
        background: purple;
        float: left;
    }
    section{
        width: 100px;
        height: 40px;
        background: maroon;
        font: right;
    }
    footer{
        height: 100px;
        background: grey;
        clear: both;
    }
    body{
        width: auto;
    }
    aside{
        width: 50%;
    }
    section{
        width: 80%;
    }
    header{
        position: absolute;
        top: 100px;
        left: 100px;
    }
    header{
        z-index: 200;
    }
    header{
        position: relative;
        top: 100px;
        left: 100px;
    }
    body{
        position: relative;
    }
    header{
        position: absolute;
        top: 0px;
        left: 0px;
    }
    body{
        width: 500px;
        margin: 0 auto;
        position: relative;
    }
</style>
<body>
    <!-- <table border="0">
        <tr>
            <td colspan="2" class="header">header</td>
        </tr>
        <tr>
            <td class="aside">aside</td>
            <td class="section">section</td>
        </tr>
        <tr>
            <td colspan="2" class="footer">footer</td>
        </tr>
    </table> -->
    <header>header</header>
    <aside>aside</aside>
    <section>section</section>
    <footer>footer</footer>
</body>
</html>